X-ray image sensor and method for fabricating the same

ABSTRACT

An X-ray image sensor having a photoelectric conversion part that converts X-ray photons into electric charges. The X-ray image sensor includes a pixel electrode for collecting the electric charges and a storage capacitor for storing the electric charges collected by the pixel electrode. The storage capacitor includes a first capacitor electrode, the pixel electrode, and a dielectric layer that is deposited on the first capacitor electrode. The pixel electrode contacts an electron transport electrode via a hole through the dielectric layer. A switching TFT controls the release of electric charges in the storage capacitor to an external circuit. The switching TFT is comprised of a gate electrode, a first insulation film, a drain electrode, and a source electrode that contacts the electron transport electrode.

[0001] This application claims the benefit of Korean Patent ApplicationNo. 1999-53712, filed on Nov. 30, 2000, which is hereby incorporated byreference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to X-ray image sensors. Moreparticularly, it relates to X-ray image sensors having a TFT (Thin FilmTransistor) array, and to a method for fabricating the same.

[0004] 2. Discussion of the Related Art

[0005] X-ray detection has been widely used for medical diagnosis. X-raydetection typically uses an X-ray film to produce a photograph.Therefore, some predetermined developing and printing procedures arerequired to produce the photograph.

[0006] However, digital X-ray image sensors that employ TFTs (Thin FilmTransistors) have been developed. Such X-ray image sensors have theadvantage that real time diagnosis can be obtained.

[0007]FIG. 1 is a schematic, cross-sectional view illustrating thestructure and operation of an X-ray image sensing device 100. Includedare a lower substrate 1, a thin film transistor 3, a storage capacitor10, a pixel electrode 12, a photoconductive film 2, a protection film20, a conductive electrode 24 and a high voltage D.C. (direct current)power supply 26.

[0008] The photoconductive film 2 produces electron-hole pairs inproportion to he strength of external signals (such as incidentelectromagnetic waves or magnetic waves). That is, the photoconductivefilm 2 acts as a converter that converts external signals, particularlyX-rays, into electric signals. Either the electrons or the holes arethen gathered by the pixel electrode 12 as charges. The pixel electrodeis located beneath the photoconductive film 2. Which charge species thatis gathered depends on the voltage (Ev) polarity that is applied to theconductive electrode 24 by the high voltage D.C. power supply 26. Thegathered species charges are accumulated in the storage capacitor 10,which is formed in connection with a grounding line. Charges in thestorage capacitor 10 are then selectively transferred through the TFT 3,which is controlled externally, to an external image display device thatforms an X-ray image.

[0009] In such an X-ray image sensing device, to detect and convert weakX-ray signals into electric charges it is beneficial to decrease thetrap state density (for the electric charge) in the photoconductive film2, and to decrease charge flow in non-vertical directions. Decreasingnon-vertical charge flow is usually accomplished by applying arelatively high voltage between the conductive electrode 24 and thepixel electrode 12.

[0010] Electric charges in the photoconductive film 2 are trapped andgathered not only on the pixel electrode 12, but also over the channelregion of the TFT 3. Even during the OFF state, the electric chargestrapped and gathered on the pixel electrode 12 and on the channel regionof the TFT 3 induce a potential difference between the TFT 3 and thepixel electrode. This has a similar effect as the TFT 3 being in the ONstate. This adversely affects the switching of the TFT 3 and increasesthe OFF state leakage current. Such can result in an undesired image.

[0011]FIG. 2 is a plan view illustrating one pixel 102 of the X-rayimage sensor panel 100. Shown are the TFT 3, a storage capacitor “S” anda pixel electrode 62 that collects charges.

[0012] The TFT 3 includes a gate electrode 31, which is formed by anelongation of a gate line 50, and a drain electrode 32, which is formedby an elongation of a drain line 52.

[0013] The storage capacitor “S” is comprised of transparent first andsecond capacitor electrodes 58 and 60. A ground line 42 acts as a commonelectrode that is shared by adjacent pixels. Also shown are firstcontact holes 54 that connects the pixel electrode 62 with a sourceelectrode 33 of the TFT 3, and a second contact hole 56 that connectsthe pixel electrode 62 with the second capacitor electrode 60.

[0014] According to the conventional art, an X-ray image sensor includesa photoelectric conversion part that produces electric charges inaccordance with received electromagnetic energy; a charge storagecapacitor “S” having a first capacitor electrode 58, a dielectric layerthat is deposited on the first capacitor electrode 58, a secondcapacitor electrode 60 on the dielectric layer, a protection film havingmultiple contact hole(s) 54 and 56 on the second capacitor electrode 60,and a pixel electrode 62 that is formed on the protection film. Thepixel electrode is in contact with the second capacitor electrode 60through the contact hole(s) 56 and collects the electric chargesproduced in the photoelectric conversion part. A switching TFT 3controls the release of the electric charges stored in the storagecapacitor “S”. The switching TFT includes a gate electrode 31, a drainelectrode 32, and a source electrode 33 that contacts the pixelelectrode 62.

[0015]FIGS. 3a to 3 f are sectional views, taken along the line m-m ofFIG. 2, that illustrate a manufacturing process.

[0016] Referring to FIG. 3a, a metal layer is deposited and patterned ona substrate 1 to form a taper-shaped gate electrode 31. The substrate 1can be a quartz substrate or a glass substrate. However, the substrate 1is beneficially a glass panel since quartz panels are relativelyexpensive. The gate electrode 31 can made of a metallic materialselected from a group comprised of Molybdenum (Mo), Tantalum (Ta),Tungsten (W), Niobium (Nb), and Antimony (Sb).

[0017]FIG. 3b illustrates the steps of depositing a first insulationfilm 102 and a semiconductor layer 104. The gate insulation film 102 isformed by a deposition of an inorganic insulation film (such as asilicon nitride (SiN₄) film or a silicon oxide(SiO_(x)) film) having4000 Å thickness. Alternatively, an organic insulation material such asBCB (benzocyclobutene) or acrylic resin can be used. After thedeposition of the first insulation film 102, a dual layer semiconductorfilm 104 comprised of an amorphous silicon layer 104 a and a dopedamorphous silicon film 104 b are deposited. Although vapor deposition orion injection can be used for the formation of the doped amorphoussilicon film 104 b, vapor deposition is usually employed.

[0018] Next, as shown FIG. 3c, a second metal layer is deposited forboth the source electrode 33 and the drain electrode 32, and for thesound line 42. That metal, beneficially Chromium (Cr) or a Cr-alloy, isthen patterned to form the source electrode 33, the drain electrode 32and the ground line 42. Moreover, the portion of the doped amorphoussilicon film 104 b between the source and drain electrodes 33 and 32 iseliminated by using the source and drain electrodes as masks. Then, afirst capacitor electrode 58 is formed over the ground line 42. Thefirst capacitor electrode 58 is beneficially comprised of a transparentelectrode material such as ITO (indium tin oxide). The region C in FIG.3c designates a switching transistor.

[0019] Referring to FIG. 3d, a silicon nitride film having a thicknessof 3000 Å forms a second insulation film 106 is deposited on the sourceand drain electrodes 33 and 32, and on the first capacitor electrode 58.The second insulating film 106 acts as protective layer for the TFT 3and as a dielectric for a capacitor that is being formed with the firstcapacitor electrode 58.

[0020] After the second insulation film 106 is deposited a secondcapacitor electrode 60 is formed on the second insulation film 105 andover the first capacitor electrode 58. Beneficially, the secondcapacitor electrode is the same size as or a little larger than thefirst capacitor electrode 58.

[0021] As shown in FIG. 3e, an insulating protection film 108 is thenformed. An organic substance such as BCB (benzocyclobutene) isbeneficially used. BCB is a material that has a lower dielectricconstant than silicon nitride, silicon oxide or acrylic resin. Afterformation of the protection film 108, first and second contact holes 54and 56 are formed through the protection film 108. The first contacthole 54 exposes a portion of the source electrode 33. The second contacthole 56 exposes a portion of the second capacitor electrode 60. Althoughthe first contact hole 54 penetrates down to the source electrode 33,the second contact hole 56 can not go as deep since the second capacitorelectrode 60 acts as an etch stop that prevents the second insulationfilm 106 from being etched.

[0022]FIG. 3f illustrates the step of forming a pixel electrode 62 (athird transparent electrode layer). The pixel electrode is formed overthe second insulation film 106 such that the pixel electrode extendsinto the first and second contact holes 54 and 56 and electricallyconnects with the source electrode and the second capacitor electrode60. In addition, the pixel electrode 62 is formed such that it extendsover the TFT 3.

[0023] The next step is the application of a light-sensitive material123. That material converts received external signals (X-rays) intoelectric charges. The light-sensitive material 123 is beneficiallycomprised of an amorphous selenium compound that is deposited in athickness of 100 to 500 μm by an evaporator. However, otherX-ray-sensitive materials that having low dark conductivity and highsensitivity to external signals, for example HgI₂, PbO₂, CdTe, CdSeThallium bromide or cadmium sulfide can also be used. When thelight-sensitive material is exposed to X-rays, electron-hole pairs areproduced in the light-sensitive material in accordance with the strengthof the x-rays.

[0024] After the application of the X-ray-sensitive material, atransparent conductive electrode 133 that passes X-ray is formed. When avoltage is applied to the transparent conductive electrode 133 whileX-rays arc being irradiated electron-hole pairs formed in thelight-sensitive material are separated into charges that are gathered tothe pixel electrode 62 and stored in the storage capacitor “S”.

[0025] According to the mentioned conventional X-ray image sensingdevice, however, the depositing and patterning of the electrodes areperformed three times to fabricating the storage capacitor “S”.Moreover, the gate line, and the source and drain electrode areoveretched while etching the ITO layers.

[0026] Moreover, as shown FIG. 4, due to the shortness of the length“ΔL” between the first capacitor electrode 58 and the source electrode33, a short-circuit can result.

[0027] Furthermore, a parasitic capacitor between the drain line 52 andthe first capacitor electrode 58 can cause problems. The presentinvention has been developed as a result of continuous effort by heinventors to solve the above-described problems.

SUMMARY OF THE INVENTION

[0028] Accordingly, the present invention is directed to an x-ray imagesensor and to a method for fabricating the same and that substantiallyobviates one or more of the problems due to limitations anddisadvantages of the related art.

[0029] An object of the present invention is to provide an X-ray imagesensor having simpler processing steps while forming ITO (indium tinoxide) electrodes.

[0030] Another object of the present invention is to provide an X-rayimage sensor having improved yields.

[0031] A further object of the invention is to provide a method offorming an X-ray image sensor which can reduce processing error duringproduction by preventing short-circuits and which can decrease noise dueto a parasitic capacitor.

[0032] Additional features and advantages of the invention will be setforth in the description which follows, and in part will be apparentfrom the description, or may be learned by practice of the invention.The objectives and other advantages of the invention will be realizedand attained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

[0033] To achieve the above objects, the present invention provides anX-ray image sensor, including: a substrate; a gate electrode on thesubstrate; a first insulation fill on the substrate that covers the gateelectrode; a semiconductor film of amorphous silicon film on the firstinsulation film over the gate electrode; a doped amorphous silicon filmon the semiconductor film; source and drain electrodes on the dopedamorphous silicon film that are spaced apart from each other; a groundline on the first insulation film that is spaced apart from the sourceand gate electrodes; a second insulation film covering the wholesubstrate and having first and second contact holes that expose portionsof the ground line and the source electrode, respectively; a firstcapacitor electrode on the second insulation film, the first capacitorelectrode having an electrical connection with the ground line throughthe first contact hole; an electron transport electrode on the secondinsulation film, the electron transport electrode having an electricalconnection with the source electrode through the second contact hole; adielectric layer covering the second insulation film, the firstcapacitor electrode and the electron transport electrode, the dielectriclayer having a third contact hole; and a pixel electrode on thedielectric layer having an electrical connection with the electrontransport electrode.

[0034] Beneficially, the pixel electrode extends over the semiconductorfilm, and the insulation layers are made of a material selected from thegroup consisting of BCB (benzocyclobutene), acryl and polyamide.Moreover, the X-ray image sensor includes a light-sensitive material onthe pixel electrode.

[0035] In order to achieve the above objects, the invention alsoprovides a method for fabricating an X-ray image sensor including:providing a substrate; forming a gate electrode on the substrate;forming a first insulation film on the substrate and that covers thegate electrode; forming a semiconductor film of amorphous silicon filmon the first insulation film over the gate electrode; forming a dopedamorphous silicon film on the semiconductor film; forming source anddrain electrodes on the doped amorphous silicon film that are spacedapart from each other, forming a channel region by eliminating the dopedamorphous silicon film between the source and drain electrodes by usingthe source and drain electrodes as a mask; forming a ground line on thefirst insulation film that is spaced apart from the source and gateelectrodes; forming a second insulation film covering the wholesubstrate; forming first and second contact holes that expose a portionof the ground line and a portion of the source electrode, respectively;forming a first capacitor electrode on the second insulation film, thefirst capacitor electrode having an electrical connection with theground line through the first contact hole; forming an electrontransport electrode on the second insulation film, the electrontransport electrode having an electrical connection with the sourceelectrode through the second contact hole; forming a dielectric layerthat covers the second insulation film, the first capacitor electrodeand the electron transport electrode; forming a third contact hole inthe dielectric layer; forming a pixel electron on the dielectric layer,the pixel electrode having an electrical connection with the electrontransport electrode; forming a light-sensitive material on the pixelelectrode; and forming a transparent conductive electrode that passesX-rays on the light-sensitive material.

[0036] The insulation layers are beneficially made of a materialselected from the group consisting of BCB (benzocyclobutene), acryl andpolyamide. The capacitor electrode and the pixel electrode arebeneficially made of transparent ITO (indium tin oxide). TheX-ray-sensitive material is beneficially one of a group consisting ofHgI₂, PbO₂, CdTe, CdSe, Thallium Bromide, and Cadmium Sulfide etc.

[0037] It is to be understood that both toe foregoing generaldescription and the following detailed description are exemplary andexplanatory and are intended to provide further explanation of theinvention as claimed.

BRIEF DESCRIPTION OF THE DRAWING

[0038] The accompanying drawings, which are included to provide afurther understanding of the invention and are incorporated in andconstitute a part of this specification, illustrate embodiments of theinvention and together with the description serve to explain theprinciples of the invention.

[0039] In the drawings:

[0040]FIG. 1 is a cross-sectional view illustrating the principle ofoperation of an X-ray image sensor;

[0041]FIG. 2 is a plan view illustrating one pixel of an X-ray imagesensor according to a conventional art;

[0042]FIGS. 3a to 3 f are processing diagrams corresponding to across-section of FIG. 2 (III-III) and sequentially illustrate themanufacture of an X-ray image sensor according to the conventional art;

[0043]FIG. 4 is an enlarged cross-sectional view illustrating a portion“G” of FIG. 3f; and

[0044]FIGS. 5a to 5 c are processing diagrams illustrating themanufacture of an X-ray image sensor according to the present invention.

DETAILED DESCRIPTION OF AN ILLUSTRATED EMBODIMENT

[0045] Reference will now be made in detail to an illustrated embodimentof the present invention, the example of which is shown in theaccompanying drawings.

[0046] According to the present invention, an X-ray image sensorcomprises a photoelectric conversion part that produces electric chargesin accordance with the received amount of light; a charge storagecapacitor having a second insulation film with a plurality of contactholes for a first capacitor electrode, the first capacitor electrode andan electron transport electrode on the second insulation film, adielectric layer deposited on the first capacitor and electron transportelectrodes, and a pixel electrode formed on the dielectric layer incontact with the electron transport electrode through a contact hole,the electron transport electrode for collecting the electric chargesproduced in the photoelectric conversion part; and a switching TFT thatcontrols the release of electric charges stored in the storagecapacitor.

[0047] The switching TFT is comprised of a gate electrode, a firstinsulation film, a drain electrode, and a source electrode that contactsthe electron transport electrode.

[0048]FIGS. 5a to 5 e are diagrams that help illustrate the process ofmanufacturing an X-ray image sensor according to the principles of thepresent invention. Such an X-ray image sensor uses only two electrodesfor a storage capacitor.

[0049] Referring to FIG. 5a, an opaque first metal layer is deposited ona substrate 1. The first metal layer is then patterned to form a gateelectrode 200.

[0050]FIG. 5b is a cross-sectional view illustrating the depositing of afirst insulation film 202 and of a semiconductor layer 208. The (gateinsulating) first insulation film 202 is formed over the substrate bydeposition. Then, a dual layer semiconductor film 208 comprised of apure amorphous silicon film 204 and of a doped amorphous silicon film206 is deposited and patterned. The semiconductor film 203 can also bemade of polycrystalline silicon.

[0051] As shown in FIG. 5c, the next step is the formation of a secondmetal layer for source and drain electrodes 212 and 210, and for aground line 214. The second metal layer is deposited on thesemiconductor layer 208 and on the first insulation layer 202. Then, thesource and drain electrodes 212 and 210 are formed such that they arespaced apart by patterning the second metal layer on the semiconductorlayer 208. The ground line 214 is also formed on the first insulationfilm 202, again by patterning the second metal layer.

[0052] After that, a portion of the doped amorphous silicon film 206between the source an drain electrodes 212 and 210 is eliminated byusing the source and drain electrodes 212 and 210 as masks. This definesa channel region “Ch”. The thin film transistor (TFT) “T” is thiscompleted. In operation the ground line 214 removes residual charge in astorage capacitor that is being formed.

[0053]FIG. 5d is a cross-sectional view illustrating the fabricationstep of a first capacitor electrode 222 and of an electron transportelectrode 224.

[0054] A second insulation film 216 that acts as a protection film isformed over the TFT an the ground line 214. After the formation of thesecond insulation film 216, first and second contact holes 220 and 218are formed through the second insulation film. The first contact hole220 exposes a portion of the ground line 214, while the second contacthole 218 exposes a portion of the source electrode 212.

[0055] Then, a first capacitor electrode 222 and an electron transportelectrode 224 are formed on the second insulation film. The electrontransport electrode 224 is formed such that it electrically contacts thesource electrode 212, while the first capacitor electrode 222 is formedsuch that it electrically contacts the ground line 214.

[0056] Organic BCB (benzocyclobutene), which is transparent material, isbeneficially used for the second insulation film 216. BCB is a materialhaving a dielectric constant less than 3, and a superior planarizingratio that results in a flat surface. An acryl or a polyamide can alsobe employed as the second insulation film 216.

[0057] Referring to FIG. 5e, a dielectric layer 226 is then formed overthe second insulation film, over the first capacitor electrode 222, andover the electron transport electrode 224. Then, a third contact hole228 is formed through the dielectric 226 such that a portion of theelectron transport electrode 224 is exposed. Then, a pixel electrode 230(alternatively referred to as a second capacitor electrode 230) isformed on the dielectric layer 226. Moreover, the pixel electrode 230 isformed such that it has an electrical connection with the electrontransport electrode 224. As the pixel electrode acts as second capacitorelectrode, the storage capacitor “Cst” is completed. The storagecapacitor “Cst” is comprised of the first capacitor electrode 222, thepixel electrode 230, and the dielectric layer 226.

[0058]FIG. 5f illustrates a step of applying a light-sensitive material232 that is used as a converter that converts an external signal(X-rays) into electron-hole pairs. Beneficially, the light-sensitivematerial 232 is an amorphous selenium compound that is deposited to athickness of 100 to 500 μm by an evaporator. Alternatively, anX-ray-sensitive material having low dark conductivity and a highsensitivity to external signals, for example HgI₂, PbO₂, CdTe, CdSe,Thallium bromide, or Cadmium sulfide can also be used. When such alight-sensitive material is exposed to X-rays, electron-hole pairs areproduced in the light-sensitive material in accordance with the strengthof the irradiated light.

[0059] After the application of the light-sensitive material 232, atransparent conductive electrode 234 that transmits X-ray is formed overthe light-sensitive material 232.

[0060] When a voltage is applied to the conductive electrode 234 whileX-rays are being irradiated, electron-hole pairs are formed in thelight-sensitive material. These pairs are separated into electrons andholes, one species of which is gathered to the pixel electrode 230 andstored as charge in the storage capacitor “Cst”.

[0061] When the gate electrode turns the TFT ON, the stored electriccharges are transferred to an external image display device (not shown)and are used to form an X-ray image.

[0062] After stopping the mentioned switching operation, the residualcharges are transferred to the ground line 214. Therefore, the groundline 214 acts as the reset switch.

[0063] The present invention provides an X-ray image sensor having asimplicity of processing steps while forming ITO (indium tin oxide)electrodes. Moreover, the present invention provides a method offabricating an X-ray image sensor that can have improved yields owing toa reduction in the processing steps.

[0064] Furthermore, the invention provides a more reliable X-ray imagesensor having fewer short-circuits between the TFT electrodes andcapacitor electrodes. Furthermore, the invention can reduce parasiticcapacitances that affect the drain line. Therefore, noise can bedecreased.

[0065] It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An X-ray image sensor, comprising: a substrate; agate electrode on the substrate; a first insulation film on thesubstrate that covers the gate electrode; an amorphous silicon filmformed on the first insulation film over the gate electrode; a dopedamorphous silicon film defining a channel region for the amorphoussilicon film on the amorphous silicon film; source and drain electrodeson the doped amorphous silicon film that are spaced apart from eachother; a ground line on the first insulation film and that is spacedapart from the source and gate electrodes; a second insulation filmcovering the ground line, the source and drain electrodes, amorphoussilicon film, the channel region, and the first insulation film, thesecond insulation film including a first contact hole that exposes aportion of the ground line and a second contact hole that exposes aportion of the source electrode; a first capacitor electrode on thesecond insulation film, the first capacitor electrode having anelectrical connection with the ground line through the first contacthole; an electron transport electrode on the second insulation film, theelectron transport electrode having an electrical connection with thesource electrode through the second contact X hole; a dielectric layercovering the second insulation film, the first capacitor electrode, andthe electron transport electrode, the dielectric layer having a thirdcontact hole that exposes a portion of the electron transport electrode;and a second capacitor electrode on the dielectric layer, the secondcapacitor electrode having an electrical connection with the electrontransport electrode through the third contact hole.
 2. An X-ray imagesensor according to claim 1, wherein the second capacitor electrodeextends over the semiconductor film.
 3. An X-ray image sensor accordingto claim 1, wherein the first and second insulation layers are made of amaterial selected from the group comprised of BCB (benzocyclobutene),acryl, and polyamide.
 4. An X-ray image sensor according to claim 1,further comprising, an X-ray-sensitive material on the second capacitorelectrode.
 5. An X-ray image sensor according to claim 4, furthercomprising an X-ray transparent material on the X-ray-sensitivematerial.
 6. An X-ray image sensor according to claim 4, wherein saidX-ray transparent material includes a material from a group consistingof amorphous selenium, HgI₂, PbO₂, CdTe, CdSe, Thallium Bromide, andCadmium Sulfide.
 7. An X-ray image sensor according to claim 1, whereinsaid electron transport electrode is comprised of indium tin oxide. 8.An X-ray image sensor according to claim 1, wherein said secondinsulation film includes a material from a group consisting ofbenzocyclobutene, and polyamide.
 9. A method for fabricating an X-rayimage sensor, comprising: forming a gate electrode on a substrate;forming a first insulation film over the substrate and the gateelectrode; forming an amorphous silicon film on the first insulationfilm and over the gate electrode; forming a doped amorphous silicon filmon the amorphous silicon film; forming source and drain electrodes onthe doped amorphous silicon film such that the source and drainelectrodes are spaced apart from each other; forming a channel region onthe amorphous silicon layer by eliminating the doped amorphous siliconfilm between the source and drain electrodes; forming a ground line onthe first insulation film such that the ground line is spaced from thesource and gate electrodes; forming a second insulation film over theground line, the channel region, the source and drain electrodes, andthe first insulation film; forming first and second contact holesthrough the second insulation film such that a portion of the groundline is exposed by the first contact hole and a portion of the sourceelectrode is exposed by the second contact hole; forming a firstcapacitor electrode on the second insulation film such that the firstcapacitor electrode is electrically connected to the ground line throughthe first contact hole; forming an electron transport electrode on thesecond insulation film, the electron transport electrode having anelectrical connection with the source electrode through the secondcontact hole; forming a dielectric layer over the second insulationfilm, the first capacitor electrode and the electron transportelectrode; forming a third contact hole through the dielectric layer;forming a second capacitor electrode on the dielectric layer such thatthe second capacitor electrode has an electrical connection with theelectron transport electrode through the third contact hole; forming alight-sensitive material on the pixel electrode; and forming an X-raytransparent conductive electrode on the light-sensitive material .
 10. Amethod fabricating, an X-ray image sensor according to claim 9, whereinthe first and second insulation layers are formed from a materialselected from the group consisting of BCB (benzocyclobutene), acryl, andpolyamide.
 11. The method for fabricating an X-ray image sensoraccording to claim 9, wherein the first capacitor electrode and thesecond capacitor electrode are formed from indium.
 12. A method forfabricating an X-ray image sensor according to claim 11, wherein thefirst capacitor electrode and the second capacitor electrode are formedfrom indium tin oxide.
 13. A method for fabricating an X-ray imagesensor according to claim 9, wherein the X-ray-sensitive material isformed from a material selected from the group consisting, of HgI₂,PbO₂, CdTe, CdSe, Thallium Bromide, and Cadmium Sulfide.
 14. A methodfor fabricating an X-ray image sensor according to claim 9, wherein theX-ray-sensitive material is formed from amorphous selenium.
 15. A methodfor fabricating an X-ray image sensor according to claim 14, whereinamorphous selenium is at least 100 μm thick.
 16. A method forfabricating, an X-ray image sensor according to claim 15, whereinamorphous selenium is less than 500 μm thick.